There is a known semiconductor photodetecting device including a base, a plurality of semiconductor photodetecting elements disposed on the base, and a plurality of bump electrodes electrically and mechanically connecting the base and each semiconductor photodetecting element (e.g., cf. Patent Literature 1). The plurality of semiconductor photodetecting elements have a planar shape having a pair of first sides opposed to each other in a first direction and a pair of second sides opposed to each other in a second direction perpendicular to the first direction. The plurality of semiconductor photodetecting elements are disposed on the base so as to be adjacent to each other in juxtaposition.